Method for mapping physical hybrid automatic repeat request indicator channel
A method for mapping a physical hybrid automatic repeat request indicator channel (PHICH) is described. The method for mapping a PHICH includes determining an index of a resource element group transmitting a repetitive pattern of the PHICH, according to a ratio of the number of available resource element groups in a symbol in which the PHICH is transmitted and the number of available resource element groups in a first or second OFDM symbol, and mapping the PHICH to the symbol according to the determined index. In transmitting the PHICH, since efficient mapping is performed considering available resource elements varying with OFDM symbols, repetition of the PHICH does not generate interference between neighbor cell IDs and performance is improved.
1. A method of a mobile station for receiving acknowledgement/negative-acknowledgement (ACK/NACK) signal through a physical automatic repeat request indicator channel (PHICH) mapped to resource element groups (REGs) in one or more orthogonal frequency division multiplexing (OFDM) symbols, the method comprising:
determining indexes of REGs to which the PHICH is mapped in the OFDM symbols; and
receiving ACK/NACK signal through the PHICH in the OFDM symbols according to the determined indexes,
wherein the indexes of REGs to which the PHICH is mapped are determined based on a ratio n′ l′i /n′ 0 or a ratio n′ l′i /n′ 1 in an OFDM symbol having index l′ i in which an i-th repetition of a PHICH group where the PHICH is included is transmitted, wherein i is an integer of 0 to 2,
wherein n′ l′i is the number of available REGs in the OFDM symbol having index l′ i in a subframe, wherein n′ 0 is the number of available REGs in a first OFDM symbol having index 0 in the subframe, wherein n′ 1 is the number of available REGs in a second OFDM symbol having index 1 in the subframe, and
wherein the number of available REGs in a specific OFDM symbol denotes the number of REGs not assigned to a physical control format indicator channel (PCFICH) among a total REGs in the specific OFDM symbol.
2. The method of claim 1 , wherein when the PHICH is transmitted through one or three OFDM symbols in the subframe, so that the first PHICH group is started from the first OFDM symbol having index 0, the indexes of REGs to which the PHICH is mapped are determined according to the ratio n′ l′i /n′ 0 .
3. The method of claim 2 , wherein when the PHICH is transmitted through one or three OFDM symbols in the subframe, the indexes of REGs to which the PHICH is mapped are determined using the following equation:
n
i
¯
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
2
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
wherein N ID cell denotes a cell ID and m′ denotes an index related to a PHICH group in which the PHICH is included.
4. The method of claim 1 , wherein when the PHICH is transmitted through two OFDM symbols in the subframe, so that the first PHICH group is started from the second OFDM symbol having index 1, the indexes of REGs to which the PHICH is mapped are determined according to the ratio n′ l′i /n′ 1 .
5. The method of claim 4 , wherein when the PHICH is transmitted through two OFDM symbols in the subframe, the indexes of REGs to which the PHICH is mapped are determined using the following equation:
n
i
¯
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
2
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
wherein N ID cell denotes a cell ID and m′ denotes an index related to a PHICH group in which the PHICH is included.
6. A mobile station for receiving acknowledgement/negative-acknowledgement (ACK/NACK) signal through a physical automatic repeat request indicator channel (PHICH) mapped to resource element groups (REGs) in one or more orthogonal frequency division multiplexing (OFDM) symbols, the mobile station comprising a processor configured to:
determine indexes of REGs to which the PHICH is mapped in the OFDM symbols; and
receive the ACK/NACK signal through the PHICH in the OFDM symbols according to the determined indexes,
wherein the indexes of REGs to which the PHICH is mapped are is determined based on a ratio n′ l′i /n′ 0 or a ratio n′ l′i /n′ 1 in an OFDM symbol having index l′ i in which an i-th repetition of a PHICH group where the PHICH is included is transmitted, wherein i is an integer of 0 to 2,
wherein n′ l′i is the number of available REGs in the OFDM symbol having index l′ i in a subframe, wherein n′ 0 is the number of available REGs in a first OFDM symbol having index 0 in the subframe, wherein n′ 1 is the number of available REGs in a second OFDM symbol having index 1 in the subframe, and
wherein the number of available REGs in a specific OFDM symbol denotes the number of REGs not assigned to a physical control format indicator channel (PCFICH) among a total REGs in the specific OFDM symbol.
7. The mobile station of claim 6 , wherein when the PHICH is transmitted through one or three OFDM symbols in the subframe, so that the first PHICH group is started from the first OFDM symbol having index 0, the indexes of REGs to which the PHICH is mapped are determined according to the ratio n′ l′i /n′ 0 .
8. The mobile station of claim 7 , wherein when the PHICH is transmitted through one or three OFDM symbols in the subframe, the indexes of REGs to which the PHICH is mapped are determined using the following equation:
n
i
¯
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
0
′
)
⌋
+
m
′
+
⌊
2
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
wherein N ID cell denotes a cell ID and m′ denotes an index related to a PHICH group in which the PHICH is included.
9. The mobile station of claim 6 , wherein when the PHICH is transmitted through two OFDM symbols in the subframe, so that the first PHICH group is started from the second OFDM symbol having index 1, the indexes of REGs to which the PHICH is mapped are determined according to the ratio n′ l′i /n′ 1 .
10. The mobile station of claim 9 , wherein when the PHICH is transmitted through two OFDM symbols in the subframe, the indexes of REGs to which the PHICH is mapped are determined using the following equation:
n
i
¯
=
{
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
)
mod
n
l
i
′
′
i
=
0
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
1
(
⌊
(
N
ID
cell
·
n
l
i
′
′
/
n
1
′
)
⌋
+
m
′
+
⌊
2
n
l
i
′
′
/
3
⌋
)
mod
n
l
i
′
′
i
=
2
wherein N ID cell denotes a cell ID and m′ denotes an index related to a PHICH group in which the PHICH is included.